Remember the duvet cover and pillowcase I made for Rodrigo's crib? The duvet cover is open on the bottom and it's slightly longer than the duvet itself, which makes it easy to tuck the ends under the mattress. The pillowcase has a simple envelope closure. Here's a tutorial for you:

2. Take the side with the selvedge and place it with the wrong side up. Fold the selvedge edge 6 cm, press in place and edgestitch. Take the other side, fold the edge 1 cm and press it place; fold it again 1 cm, press and edgestitch.

3. Place the rectangle on top of a flat surface with the right side of the fabric facing up. Measure 12 cm from the end that has no selvedge. Grab the other end and fold it upwards up to the point where it meets the 12 cm you just measured — this means you'll be folding it 40 cm (the length of the pillow). Then fold down the other end, placing it on top of the end that you just folded (see pictures below).